SYNTHESIS AND CHARACTERIZATION OF LANTHANIDE(II) ARYLOXIDES INCLUDINGTHE FIRST STRUCTURALLY CHARACTERIZED EUROPIUM(II) COMPOUND 6)H(2)BU(2)(T)-2,6-ME-4)(2)(THF)(3)]CENTER-DOT-THF (THF=TETRAHYDROFURAN)

The lanthanide(II) aryloxide complexes [Yb(OC(6)H(2)Bu(2)(t)-2,6-Me-4) (2)(OEt(2))(2)] 1, [Yb(OC(6)H(3)Bu(2)(t)- 2,6)(2)(thf)(3)] 2, [Yb(OC(6 )H(2)Bu(3)(t)-2,4,6)(2)(thf)(3)] 3, [Sm(OC(6)H(2)Bu(2)(t)-2,6-Me-4)(2) (thf)(3)] 4, [Eu(OC(6)H(2)Bu(2)(t)- 2,6-Me-4)(2)(thf)(3)].thf 5, [Yb(O C(6)H(2)Bu(2)(t)-2,6-Me-4)(2)(thf)(3)] 6 and [Yb(OC(6)H(2)Bu(2)(t)-2,6 -Me-4)l(thf)(x)] 7 (thf = tetrahydrofuran) have been synthesized. Each of the complexes 1-3 was prepared by the reaction of 2 equivalents of the appropriate potassium aryloxide with Ybl(2) in diethyl ether (1) or thf (2 or 3). Complexes 4-6 were prepared by the reaction of 2 equi valents of K(OC(6)H(2)Bu(2)(t)-2,6-Me-4) with Lnl(2)(thf)(2) (Ln = Sm, Eu or Yb) in thf. Reacting Ybl(2) with 1 equivalent of K(OC(6)H(2)Bu( 2)(t)-2,6-Me-4) in thf yielded complex 7 as the main product, but Yb-1 71-{H-1} NMR spectroscopy showed that 6 and [Ybl(2)(thf)(4)] 8 were al so formed. The crystal structure of complex 5 reveals that it adopts a distorted trigonal-bipyramidal conformation with (i) apical thf oxyge ns [O(4)-Eu-O(5) 178.6(2)degrees, Eu-O(4) 2.590(5) and Eu-O(5) 2:573(5 ) Angstrom]; (ii) the equatorial O(1), O(2) and O(3) thf coplanar; and (iii) Eu-O(1) 2.321(5), Eu-O(2) 2.337(5) and Eu-O(3) 2.515(6) Angstro m. The crystal structure of complex 8 showed there to be an octahedral arrangement around the metal, the molecule lying on a crystallographi c inversion centre, with angles l-Yb-O(1) 90.1(2), l-Yb-O(2) 91.4(2) a nd O(1)-Yb-O(2) 88.9(3)degrees, and bond lengths Yb-l 3.103(1). Yb-O(1 ) 2.399(9) and Yb-O(2) 2.373(8) Angstrom.